<template>
	<view class="u-wrap">
		<!-- 搜索组件 -->
		<my-search></my-search>
		<!-- 滑动view -->
		<view class="u-menu-wrap">
			<!-- 左边一级分类 -->
			<scroll-view scroll-y="true" :style="{height: wh + 'px'}" class="u-tab-view menu-scroll-view"
				:scroll-top="scrollTop" :scroll-into-view="itemId">
				<view v-for="(item,index) in cateList" :key="index" class="u-tab-item"
					:class="[current == index ? 'u-tab-item-active' : '']" @tap.stop="swichMenu(index)">
					<!-- 一级分类标题 -->
					<text class="u-line-1">{{item.name}}</text>
				</view>
			</scroll-view>
			<!-- 右边二级分类 -->
			<scroll-view :scroll-top="scrollRightTop" scroll-y scroll-with-animation class="right-box"
				@scroll="rightScroll" :style="{height: wh + 'px'}">
				<view class="page-view">
					<view class="class-item" :id="'item' + index" v-for="(item , index) in cateList" :key="index">
						<view class="item-title">
							<view class="item-line line1"></view>
							<text>{{item.name}}</text>
							<view class="item-line line2"></view>
						</view>
						<view class="item-container">
							<view class="thumb-box" v-for="(item1, index1) in item.children" :key="index1">
								<!-- 二级分类图片 -->
								<image @click="goGoodsList(item1)" class="item-menu-image" :src="item1.sid_image">
								</image>
								<!-- 二级分类标题 -->
								<view class="item-menu-name">{{item1.title}}</view>
							</view>
						</view>
					</view>
				</view>
			</scroll-view>
		</view>
	</view>
</template>

<script>
	// 导入api
	import api from "../../api/api.js"
	export default {
		data() {
			return {
				// 当前可用的高度
				wh: 0,
				// 默认当前现在第一个一级分类
				active: 1,
				// 一级分类列表
				cateList: [],
				scrollTop: 0, //tab标题的滚动条位置
				oldScrollTop: 0, // tab标题的滚动条旧位置
				current: 0, // 预设当前项的值
				menuHeight: 0, // 左边菜单的高度
				menuItemHeight: 0, // 左边菜单item的高度
				itemId: '', // 栏目右边scroll-view用于滚动的id
				arr: [], // 储存距离顶部高度的数组
				scrollRightTop: 0, // 右边栏目scroll-view的滚动条高度
				timer: null // 定时器
			}
		},
		onReady() {
			this.getMenuItemTop()
		},
		methods: {
			getMenuItemTop() {
				new Promise(resolve => {
					let selectorQuery = uni.createSelectorQuery();
					selectorQuery.selectAll('.class-item').boundingClientRect((rects) => {
						// 如果节点尚未生成，rects值为[](因为用selectAll，所以返回的是数组)，循环调用执行
						if (!rects.length) {
							setTimeout(() => {
								this.getMenuItemTop();
							}, 10);
							return;
						}
						rects.forEach((rect) => {
							// 视情况而定，这里减去rects[0].top，是因为第一项顶部可能不是贴到导航栏(比如有个搜索框的情况)
							// this.arr.push(rect.top - rects[0].top);
							this.arr.push(rect.top)
							resolve();
						})
					}).exec()
				})
			},
			getElRect(elClass, dataVal) {
				new Promise((resolve, reject) => {
					const query = uni.createSelectorQuery().in(this);
					query.select('.' + elClass).fields({
						size: true
					}, res => {
						// 如果节点尚未生成，res值为null，循环调用执行
						if (!res) {
							setTimeout(() => {
								this.getElRect(elClass);
							}, 10);
							return;
						}
						this[dataVal] = res.height;
						resolve();
					}).exec();
				})
			},
			getMenuItemTop() {
				new Promise(resolve => {
					let selectorQuery = uni.createSelectorQuery();
					selectorQuery.selectAll('.class-item').boundingClientRect((rects) => {
						// 如果节点尚未生成，rects值为[](因为用selectAll，所以返回的是数组)，循环调用执行
						if (!rects.length) {
							setTimeout(() => {
								this.getMenuItemTop();
							}, 10);
							return;
						}
						rects.forEach((rect) => {
							// 视情况而定，这里减去rects[0].top，是因为第一项顶部可能不是贴到导航栏(比如有个搜索框的情况)
							// this.arr.push(rect.top - rects[0].top);
							this.arr.push(rect.top)
							resolve();
						})
					}).exec()
				})
			},
			async observer() {
				this.tabbar.map((val, index) => {
					let observer = uni.createIntersectionObserver(this);
					observer.relativeTo('.right-box', {
						top: 0
					}).observe('#item' + index, res => {
						if (res.intersectionRatio > 0) {
							let id = res.id.substring(4);
							this.leftMenuStatus(id);
						}
					})
				})
			},
			async leftMenuStatus(index) {
				this.current = index;
				// 如果为0，意味着尚未初始化
				if (this.menuHeight == 0 || this.menuItemHeight == 0) {
					await this.getElRect('menu-scroll-view', 'menuHeight');
					await this.getElRect('u-tab-item', 'menuItemHeight');
				}
				// 将菜单活动item垂直居中
				this.scrollTop = index * this.menuItemHeight + this.menuItemHeight / 2 - this.menuHeight / 2;
			},
			async swichMenu(index) {
				if (this.arr.length == 0) {
					await this.getMenuItemTop();
				}
				if (index == this.current) return;
				this.scrollRightTop = this.oldScrollTop;
				this.$nextTick(function() {
					this.scrollRightTop = this.arr[index];
					this.current = index;
					this.leftMenuStatus(index);
				})
			},
			async rightScroll(e) {
				this.oldScrollTop = e.detail.scrollTop;
				if (this.arr.length == 0) {
					await this.getMenuItemTop();
				}
				if (this.timer) return;
				if (!this.menuHeight) {
					await this.getElRect('menu-scroll-view', 'menuHeight');
				}
				setTimeout(() => { // 节流
					this.timer = null;
					// scrollHeight为右边菜单垂直中点位置
					// let scrollHeight = e.detail.scrollTop + this.menuHeight / 2;
					// scrollHeight为右边菜单头部位置
					let scrollHeight = e.detail.scrollTop + 20;
					for (let i = 0; i < this.arr.length; i++) {
						let height1 = this.arr[i];
						let height2 = this.arr[i + 1];
						if (!height2 || scrollHeight >= height1 && scrollHeight < height2) {
							this.leftMenuStatus(i);
							return;
						}
					}
				}, 10)
			},
			// 跳转商品列表页面
			goGoodsList(item) {
				uni.navigateTo({
					url: `/pages/goods/goods_list/goods_list?sid=${item.sid}&title=${item.title}`,
				})
			}
		},
		onLoad() {
			// 获取当前可用高度
			const sysInfo = uni.getSystemInfoSync();
			this.wh = sysInfo.windowHeight;
			// 获取一级分类数据
			api.getOneCate().then(res => {
				// 获取失败
				if (res.data.status != 200) return uni.$showMsg(res.data.data.err);
				// 获取成功
				this.cateList = res.data.data.cateOneList;
				for (var i = 0; i < this.cateList.length; i++) {
					// 将字符串数组转换
					res.data.data.cateOneList[i].children = JSON.parse(res.data.data.cateOneList[i].children);
				}
				uni.$showMsg(res.data.msg);
			});
		},
	}
</script>

<style>
	/* ------------------ */
	.u-menu-wrap {
		flex: 1;
		display: flex;
		overflow: hidden;
	}

	.u-tab-view {
		width: 200rpx;
	}

	.u-tab-item {
		height: 110rpx;
		background: #f6f6f6;
		box-sizing: border-box;
		display: flex;
		align-items: center;
		justify-content: center;
		font-size: 26rpx;
		color: #444;
		font-weight: 400;
		line-height: 1;
	}

	.u-tab-item-active {
		position: relative;
		color: #1db0fc;
		font-size: 12px;
		font-weight: 500;
		background: white;
	}

	.u-tab-item-active::before {
		content: "";
		position: absolute;
		border-left: 4px solid #1db0fc;
		height: 52rpx;
		left: 0;
		top: 29rpx;
	}

	.u-tab-view {
		height: 100%;
	}

	.right-box {
		background-color: rgb(250, 250, 250);
	}

	.page-view {
		background-color: white;
	}

	.class-item {
		border-radius: 8rpx;
		font-size: 12px;
		font-weight: bold;
		text-align: center;
		padding: 15px 0;
	}

	.class-item:last-child {
		min-height: 100vh;
	}

	.item-title {
		font-size: 12px;
		font-weight: bold;
		text-align: center;
		padding: 15px 0;
		display: flex;
		justify-content: center;
		align-items: center;
	}

	.item-line {
		width: 53px;
		height: 1px;
		background-color: #f0f0f0;
	}

	.line1 {
		margin-right: 15px;
	}

	.line2 {
		margin-left: 15px;
	}

	.item-menu-name {
		margin-top: 8rpx;
		font-weight: normal;
		font-size: 12px;
		color: $u-main-color;
	}

	.item-container {
		display: flex;
		flex-wrap: wrap;
	}

	.thumb-box {
		width: 33.3%;
		display: flex;
		align-items: center;
		justify-content: center;
		flex-direction: column;
		margin-top: 15px;
	}

	.item-menu-image {
		width: 120rpx;
		height: 120rpx;
	}
</style>